Method of installing a structural blind fastener

ABSTRACT

A two-piece, one-sided-installation fastener system may have an internally-threaded sleeve having a shank and a sleeve head. The fastener system may include an externally-threaded core bolt having a frangible driving provision and a core bolt head.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of and claimspriority to pending U.S. application Ser. No. 13/674,055 filed on Nov.11, 2012, and entitled STRUCTURAL BLIND FASTENER AND METHOD OFINSTALLATION, the entire contents of which is expressly incorporated byreference herein.

FIELD

The present disclosure relates generally to fasteners and, moreparticularly, to a blind structural fastener and the installationthereof in a structure.

BACKGROUND

Mechanical fasteners are widely used for joining two or more componentsof a structural assembly. For example, mechanical fasteners are usedextensively for joining the structural components of an airframe.One-sided-installation fasteners or blind fasteners may be used inapplications where access to one side of a structural assembly isunavailable. One-sided-installation fasteners may be inserted into ahole and a portion of the fastener on the blind side of the hole may bedeformed. The deformed portion of the fastener on the blind side of thehole provides a bearing feature to induce preload in the fastener suchthat the components of the structural assembly may be clamped together.

Certain types of existing one-sided-installation fasteners may providefor a relatively large bearing area on the blind side of the hole.Unfortunately, such fasteners may either lack the ability to induce arelatively high level of preload in the fastener or such fasteners mayprovide for a relatively small amount of thickness variation or griprange of the clamped components. Other types of existingone-sided-installation fasteners may provide a relatively high level offastener preload or a relatively large grip range of the clampedcomponents. However, such fasteners may provide a small amount ofbearing area which may limit the tension capability of the fastenedjoint.

Still other types of existing one-sided-installation fasteners may allowfor a relatively large grip range of the clamped components or arelatively large amount of bearing area on the blind side of the hole.However, such fasteners may induce a relatively low level of preload inthe fastener. Furthermore, the process of installing certainone-sided-installation fasteners may result in the twisting and/orinconsistent plastic deformation of the deformed portion of the fastenerwhich may reduce the repeatability of the preload level from fastener tofastener.

Additionally, certain one-sided-installation fasteners having separatecomponents for the head and the blind side feature may allow thedeformed portion to rotate during installation which may cause damage tothe structure. Furthermore, in certain one-sided-installation fasteners,the blind side formations may form in a manner allowing axial loads toproduce further deformation after installation of the fastener iscomplete. For example, certain one-sided-installation fasteners may havean open-ended deformable portion. Excessive axial loading of thestructure after the fastener is installed may result in furtherdeformation of the deformed portion. Unfortunately, when the axial loadis removed, the fastener joint may exhibit looseness in the axialdirection as a result of the deformation of the open-ended deformedportion.

As can be seen, there exists a need in the art for aone-sided-installation fastener that provides for a relatively largebearing area on the blind side of the hole, a relatively high level ofpreload in the fastener, and a relatively large amount of thicknessvariation of the clamped components. In addition, there exists a need inthe art for a one-sided-installation fastener with minimal ornon-existent twisting of the deformed portion of the fastener duringinstallation, and wherein the fastener is prevented from rotatingrelative to the structure during fastener installation, and the fastenerresists additional deformation of the deformed portion afterinstallation.

SUMMARY

The above-noted needs associated with fastener systems are addressed andalleviated by the present disclosure, which, in a configuration,provides a two-piece, one-sided-installation fastener system having aninternally-threaded sleeve having a shank and a sleeve head. Thefastener system also includes an externally-threaded core bolt having afrangible driving provision and a core bolt head.

In a further configuration, disclosed is a fastener system having aninternally-threaded sleeve having a shank and a sleeve head. Thefastener system includes an externally-threaded core bolt having afrangible driving provision and a core bolt head. The sleeve may have anannealed portion extending along a portion of a sleeve length. Thefrangible driving provision may include a rotation feature and/or anaxial translation feature for respectively rotating and axiallytranslating the core bolt relative to the sleeve.

Also disclosed is a method of installing a two-piece,one-sided-installation fastener system including the steps of insertinga core bolt and a sleeve into a hole having a front side and a backside. The core bolt may have a frangible driving provision coupled to acore bolt head. The method may further include translating the core boltbackward away from the front side of the hole, and buckling a softenedportion of the sleeve to form a buckled sleeve portion. The method mayadditionally include flattening the buckled sleeve portion against theback side of the hole, and rotating the core bolt relative to the sleeveto apply or increase tension preload in the fastener system.

The features, functions, and advantages that have been discussed can beachieved independently in various configurations of the presentdisclosure or may be combined in yet other configurations, furtherdetails of which can be seen with reference to the following descriptionand drawings below.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the present disclosure will become moreapparent upon reference to the drawings wherein like numerals refer tolike parts throughout and wherein:

FIG. 1 is a side view of a core bolt of a two-piece,one-sided-installation fastener system;

FIG. 2 is an end view of the core bolt having a frangible drivingprovision included with the core bolt head;

FIG. 3 is a sectional side view of a sleeve of the two-piece,one-sided-installation fastener system having a softened portion along aportion of a length of the sleeve;

FIG. 4 is an end view of the sleeve;

FIG. 5 is a sectional side view of the core bolt assembled with thesleeve prior to installation in a hole in a structure;

FIG. 6 is a sectional side view of the core bolt and sleeve installed inthe structure and illustrating a minimum grip and a maximum gripcapability of the fastener system;

FIG. 7 is a sectional side view of the fastener system in a maximum gripinstallation and illustrating the frangible driving provision and corebolt being axially translated backward away from a front side of thestructure and buckling of the softened portion of the sleeve;

FIG. 8 is a sectional side view of the fastener system in a minimum gripinstallation and illustrating the frangible driving provision and corebolt axially translated backward away from the front side of thestructure and buckling of the softened portion of the sleeve;

FIG. 9 is a sectional side view of the fastener system illustratingrotation of the frangible driving provision and the core bolt relativeto the sleeve to apply a tension in the fastener system for minimum andmaximum grip installations;

FIG. 10 is a sectional side view of the core bolt, sleeve, and structureand further illustrating the separation of the frangible drivingprovision from the core bolt head at a pre-defined fastener preload forminimum and maximum grip installations;

FIG. 11 is a sectional side view of a configuration of an installationtool;

FIG. 12 is an end view of the installation tool;

FIG. 13 is a sectional end view of the installation tool;

FIG. 14 is a sectional side view of a further configuration of aninstallation tool;

FIG. 15 is a side view of a frangible driving provision configuredcomplementary to the installation tool shown in FIG. 14;

FIG. 16 is a side view of a configuration of a frangible drivingprovision;

FIG. 17 is an end view of the frangible driving provision shown in FIG.16;

FIG. 18 is a sectional side view of a further configuration of aninstallation tool;

FIG. 19 is a side view of a frangible driving provision configuredcomplementary to the installation tool shown in FIG. 18;

FIG. 20 is a sectional side view of a further configuration of aninstallation tool;

FIG. 21 is a sectional end view of the installation tool shown in FIG.20;

FIG. 22 is a side view of a frangible driving provision configuredcomplementary to the installation tool shown in FIG. 20;

FIG. 23 is a flow diagram including one or more operations that may beincluded in a method of installing a two-piece, one-sided-installationfastener system;

FIG. 24 is a flow diagram of an aircraft manufacturing and servicemethodology; and

FIG. 25 is a block diagram of an aircraft.

DETAILED DESCRIPTION

Referring now to the drawings wherein the showings are for purposes ofillustrating preferred and various configurations of the disclosure,shown in FIG. 1 is a side view of a core bolt 150 of a two-piece,one-sided-installation fastener system 100. FIG. 3 is a side view of asleeve 104 that may be sized and configured to be assembled with thecore bolt 150 of FIG. 1 for installation in a hole 302 of a structure300 (FIG. 5). In FIG. 1, the core bolt 150 may include a core bolt head152 having a core bolt shank 158. The core bolt shank 158 may haveexternal core bolt threads 160 formed along at least a portion of alength of the core bolt shank 158 and terminating at a core bolt end162. Although the core bolt shank 158 is shown as being substantiallydevoid of threads along a majority of the core bolt length 164, the corebolt shank 158 may be threaded along any portion of the core bolt length164 from the core bolt head 152 to the core bolt end 162.

In FIG. 1, the core bolt threads 160 may be formed at a smaller diameterthan the core bolt diameter 166. However, the core bolt threads 160 maybe formed at any diameter relative to the core bolt diameter 166. Thecore bolt 150 is shown as having a countersunk head 156 having a corebolt bearing surface 154 with a tapered configuration. However, the corebolt head 152 may be provided in any configuration including aprotruding head configuration (not shown) wherein the core bolt bearingsurface 154 may have a generally flat or non-tapered configuration.

In FIG. 1-2, a frangible driving provision 180 may be included with thecore bolt head 152. In a configuration, the frangible driving provision180 may be integrally formed with the core bolt head 152 and the corebolt shank 158. The frangible driving provision 180 may have a generallyelongated shape and may protrude outwardly from the core bolt head 152.The frangible driving provision 180 may be generally aligned with afastener axis 102 of the core bolt 150 and may have a generally smallerouter diameter than the core bolt head 152.

The frangible driving provision 180 may include an axial translationfeature 192 and a rotation feature 186. The axial translation feature192 may be configured to facilitate axial translation or displacement ofthe core bolt head 152 along a backward direction away from a front side304 (FIG. 5) of the structure 300 (FIG. 5) to cause buckling of asoftened portion 132 (FIG. 5) of the sleeve 104 (FIG. 3) against a backside 306 (FIG. 5) of the structure 300 during an initial part of theinstallation of the fastener system 100. The rotation feature 186 may beconfigured to rotate the core bolt 150 relative to the sleeve 104 toapply a tension preload in the fastener system 100 after the buckling ofthe softened portion 132 against the back side 306 of the structure 300as described in greater detail below.

In FIG. 2, the axial translation feature 192 may comprise at least oneof helical threads 194 (FIG. 15), annular grooves 196, or other geometrythat may be formed on the frangible driving provision 180 for axiallytranslating the core bolt 150. The helical threads 194 may be formed onan exterior of the frangible driving provision 180 and may be configuredto be engaged by an installation tool 400 (FIGS. 11-14) for installingthe fastener system 100. For example, the helical threads 194 may beformed at the same thread pitch and thread size as the internal threadsof a collet 410 of an installation tool 400 (FIGS. 11-14) as describedbelow. The helical threads 194 may be interrupted by a pair of opposingflats of the rotation feature 186 of the frangible driving provision180, or the helical threads 194 may be continuous (not shown) around thefrangible driving provision 180. The helical threads 194 may be formedat a length that allows for sufficient engagement by the collet 410threads such that the installation tool 400 may transfer an axial load(not shown) of sufficient magnitude to the frangible driving provision180 to flatten the buckled sleeve portion 138 against the back side 306of the structure 300 as shown in FIGS. 7-8.

The axial translation feature 192 may optionally comprise annulargrooves 196 (FIGS. 1, 19, and 22) that may be configured complementaryto a collet 410 (FIGS. 18 and 20) of an installation tool 400 such thatthe collet 410 may grip the annular groves 196 and axially translate thecore bolt 150 away from the front side 304 of the structure 300. Theannular grooves 196 in FIG. 19 may be formed at a groove pitch anddiameter that is complementary to the collet 410 in FIG. 18. Inaddition, the annular grooves 196 may be configured to facilitaterelease of the frangible driving provision 180 from the collet 410 whenthe frangible driving provision 180 fractures off of the core bolt head152 as illustrated in FIG. 10 and described below. For example, althoughnot shown, the annular grooves 196 may have ramped surfaces to allow thecollet 410 to slidably release the frangible driving provision 180 afterfracturing off of the core bolt head 152.

Although shown as being formed on an exterior of the frangible drivingprovision 180, the axial translation feature 192 may be formed on aninterior of the frangible driving provision 180 such as within a bore(not shown) that may be formed within the frangible driving provision180. The rotation feature 186 may comprise one or more faceted surfaces188 or other features formed on the interior or exterior of thefrangible driving provision 180 and configured to facilitate rotation ofthe frangible driving provision 180 and the core bolt 150. For example,FIG. 2 illustrates the frangible driving provision 180 having externalfaceted surfaces 188 comprising opposing flats 190 for receiving arotational drive member (e.g., a rotational socket with a rectangularslot—not shown) of an installation tool described below.

The frangible driving provision 180 may be configured to be separatedfrom the core bolt head 152 following the application of tension preloadin the fastener system 100. For example, the frangible driving provision180 may comprise a frangible pintail 182 having a break groove 184 at aninterface 198 between the frangible pintail 182 and the core bolt head152. The break groove 184 may provide a reduced cross sectional area atthe interface 198 relative to the cross sectional area along a remainderof the frangible pintail 182.

Referring to FIG. 3, shown is a side view of the sleeve 104 of thetwo-piece, one-sided-installation fastener system 100. The sleeve 104may have a sleeve head 106 and a sleeve shank 114 having a generallyhollow tubular configuration extending from the sleeve head 106 to asleeve tail 126 and defining a sleeve length 118. The sleeve 104 mayhave a sleeve inside diameter 122 sized complementary to the core boltdiameter 166 (FIG. 1). The sleeve 104 may have a sleeve outside diameter120 that may be sized complementary to the diameter of a hole 302 (FIG.5) in the structure 300 (FIG. 5). For example, the sleeve outsidediameter 120 may be sized and configured to provide a clearance fit oran interference fit with a hole 302 in the structure 300 (FIG. 5) asdescribed below. The sleeve shank 114 may be provided in a sleeve wallthickness 124 that may be dictated in part by the sleeve outsidediameter 120. For example, for a sleeve outside diameter 120 ofapproximately 0.25 inch, the sleeve wall thickness 124 may beapproximately 0.015 to 0.030 inch. For a sleeve outside diameter 120 ofapproximately 0.38 inch, the sleeve wall thickness 124 may beapproximately 0.030 to 0.050 inch. However, the sleeve 104 may beprovided in any sleeve wall thickness 124 and is not limited to theabove noted ranges.

In FIG. 3, the sleeve 104 may include a softened portion 132 such as anannealed portion extending along at least a portion of the sleeve length118. The softened portion 132 may be positioned along the sleeve length118 such that the softened portion 132 may be buckled against the backside 306 (FIG. 5) of the structure 300 to form a buckled sleeve portion138 (FIG. 7). The softened portion 132 may be annularly-shaped orband-shaped and may have increased ductility, increased softness,increased propensity to buckle under axially-compressive loading, and/orincreased formability relative to the ductility, softness, propensity tobuckle, or formability of the sleeve 104 at locations outside of thesoftened portion 132. The softened portion 132 may be formed in thesleeve 104 by any one of a variety of different means including, but notlimited to, localized heat treatment or annealing of the sleeve 104 suchas by using an inductive coil (not shown) placed over the sleeve 104 ata location where softening of the sleeve 104 material is desired. Thesoftened portion 132 may also be formed in the sleeve 104 by varying thesleeve cross-section (not shown) such as with a reduced sleeve wallthickness (not shown) which may provide an increased propensity forbuckling under axial loading. However, the softened portion 132 may beformed in the sleeve 104 in any one of a variety of different means andis not limited to annealing by localized heat treatment.

In FIG. 3, the sleeve shank 114 may include internal sleeve threads 116formed on an end of the sleeve 104. The internal sleeve threads 116 maybe formed complementary to the core bolt threads 160 and may terminateat the sleeve tail 126. The sleeve tail 126 may include a lockingfeature 128 configured to restrict rotation of the core bolt 150relative to the sleeve 104 such as after installation of the fastenersystem 100 in a structure. The locking feature 128 may comprise a sleeveannular groove 130 that may be formed on the sleeve shank 114 adjacentthe sleeve tail 126. However, the locking feature 128 may be configuredin any one of a variety of different configurations and is not limitedto a sleeve annular groove 130. In this regard, the locking feature 128may comprise any mechanism that may restrict rotation of the core boltthreads 160 relative to the internal sleeve threads 116. For example,the locking feature 128 may comprise a nylon patch formed on theinternal sleeve threads 116 adjacent the sleeve tail 126. Alternatively,the locking feature 128 may comprise a local deformation of the internalsleeve threads 116 to restrict rotation of the core bolt 150 relative tothe sleeve 104 following installation of the fastener system 100 withina structure.

Referring to FIGS. 3-4, the sleeve 104 is shown as having a countersunkhead 110 having a sleeve bearing surface 108 with a taperedconfiguration for bearing against a structure 300 (FIG. 5). However, thesleeve head 106 may be provided in a protruding head configuration (notshown) wherein the sleeve bearing surface 108 may be generally flatand/or parallel to a surface of the structure 300. In this regard, thesleeve head 106 may be provided in any configuration and is not limitedto a countersunk head configuration or a protruding head configuration.The sleeve head 106 may include a core bolt pocket 112 that may be sizedand configured to receive the core bolt head 152. In the configurationshown, the sleeve head 106 is sized and configured to receive a corebolt 150 having a countersunk configuration as shown in FIG. 1. However,as indicated above, the sleeve head 106 and the core bolt head 152 maybe provided in any one of a variety of combinations of a countersunkhead, a protruding head (not shown), or other head configurations.

In FIG. 4, the sleeve head 106 may include an anti-rotation feature 134to provide a means for preventing rotation of the sleeve 104 relative tothe core bolt 150 and/or relative to a hole 302 (FIG. 5) in thestructure 300 (FIG. 5) during installation of the fastener system 100.For example, the sleeve head 106 may include one or more indentations orprotrusions 136 that may be sized and configured to be engaged by aninstallation tool (not shown) to prevent rotation of the sleeve 104relative to the core bolt 150 and/or a hole 302 (FIG. 5) through whichthe sleeve 104 extends.

The sleeve 104 and the core bolt 150 may be formed of any one of avariety of different materials including any metallic material and/ornonmetallic material. For example, the core bolt 150 and/or the sleeve104 may be formed of titanium alloys including 6-6-2 Ti, 6-4 Ti, 3-8 Tiand other titanium alloys. The core bolt 150 and/or the sleeve 104 mayalso be formed of steel and/or stainless steel including stainless steelalloys such as A286, A304, and A266 CRES or other stainless steelalloys. The core bolt 150 and/or the sleeve 104 may also be formed ofinconel, nickel, cobalt and any alloys or combinations thereof.

Referring to FIG. 5, shown is the core bolt 150 assembled with thesleeve 104 prior to installation of the core bolt 150/sleeve 104assembly into a hole 302 of a structure 300. The structure 300 may havea front side 304 and a back side 306. The core bolt 150 is preferablysized such that the core bolt shank 158 of the core bolt 150 is notengaged in the locking feature 128 of the sleeve 104 when the fastenersystem 100 is initially installed in the hole 302 and prior to axiallytranslating the core bolt 150. In FIG. 5, the locking feature 128 of thesleeve 104 may occupy approximately 2-3 or more of the internal sleevethreads 116. The softened portion 132 of the sleeve 104 is preferablypositioned along the sleeve length 118 such that at least a part of thesoftened portion 132 lies beneath the surface of the back side 306 ofthe structure 300, as described in greater detail below.

In FIG. 5, the front side 304 of the structure 300 may have a structurebearing surface 308 that may be configured complementary to the sleevebearing surface 108. For example, for a sleeve head 106 having acountersunk configuration with a tapered bearing surface, the structurebearing surface 308 may likewise be tapered. The hole 302 may have ahole 302 diameter that is preferably sized and configured complementaryto the sleeve outside diameter 120. The hole 302 may be sized andconfigured to provide a clearance fit with the sleeve outside diameter120 or to provide an interference fit with the sleeve outside diameter120. In a configuration, the fastener system 100 may be installed bycoating the sleeve 104 with a sealant prior to insertion into a hole 302of a structure 300. For example, for installing a metallic sleeve104/core bolt 150 assembly within a composite structure 300, the sleeve104 may be coated with a wet sealant to protect against galvaniccorrosion. The sleeve 104 may also include one or more types of coatingsas part of its finished state. Such coatings may reduce friction duringinsertion of the sleeve 104 into a hole 302 (e.g., an interference fithole) or for ease of installation in other types of holes such asclearance holes. Such coatings may comprise a lubricious coating such asan aluminum pigmented coating, dry film lubricant (e.g., molybdenumdisulfide), or any one of a variety of other types of coatings.

Referring to FIG. 6, shown is a side view of the core bolt 150 andsleeve 104 installed in the structure 300 and illustrating a minimumgrip 312 and a maximum grip 310 capability of the fastener system 100.FIG. 6 illustrates a structure 300 shown in solid lines representing aminimum grip 312 application for the fastener system 100. In a minimumgrip 312 application, the sleeve 104 may be configured such that thesoftened portion 132 of the sleeve 104 extends above and below thesurface of the back side 306 of the structure 300 to allow for bucklingof the softened portion 132 against the back side 306. FIG. 6 alsoillustrates a structure 300 shown in phantom lines representing amaximum grip 310 application for the fastener system 100. In a maximumgrip 310 application, the sleeve 104 may be configured such that thesoftened portion 132 of the sleeve 104 extends above and below the backside 306 of the structure 300 to allow for buckling of the softenedportion 132 against the back side 306.

Advantageously, the presently-disclosed fastener system 100 may beinstalled for a relatively large grip range 314 (e.g., large thicknessvariation) of structure 300. For example, a single configuration of thepresently-disclosed fastener system 100 may include a softened portion132 that provides for a grip range 314 of at least 0.10 inch. Such arelatively large grip range 314 provided by the presently-disclosedfastener system 100 advantageously minimizes the quantity of differentfastener lengths that must be maintained in stock in comparison to thelarger quantity of different fastener lengths that must be maintained instock for conventional fastener systems having a relatively small griprange 314 (e.g., 0.050 or 0.063 inch). Additionally, a relatively largegrip range may provide additional grip capability where installationsmay occur outside of the expected structural thicknesses due tostructure manufacturing tolerances.

Referring to FIG. 7, shown is a side view of the fastener system 100 inan initial stage of installation in a maximum grip 310 application. Thefrangible driving provision 180 and the core bolt 150 are axiallytranslated along a backward direction away from a front side 304 of thestructure 300. The axial translation of the core bolt 150 may beprovided by engaging the axial translation feature 192 of the frangibledriving provision 180 with an installation tool as described below. Thesleeve head 106 may be maintained in contact with the structure bearingsurface 308 (FIG. 5) during axial translation of the core bolt 150.Displacement of the core bolt head 152 away from the front side 304results in buckling of the softened portion 132 against the back side306 of the structure 300. The softened portion 132 may buckle radiallyoutwardly into a flattened, annularly-shaped, buckled sleeve portion 138against the back side 306 of the structure 300.

Referring to FIG. 8, shown is a side view of the fastener system 100during installation in a minimum grip 312 application. The core bolthead 152 is displaced at a greater distance away from the front side 304of the structure 300 relative to the amount of core bolt head 152displacement for the maximum grip 310 application shown in FIG. 7. Inaddition, the buckled sleeve portion diameter 140 for the minimum grip312 application shown in FIG. 8 is larger than the buckled sleeveportion diameter 140 of the maximum grip 310 application shown in FIG.7.

Advantageously, the sleeve 104 may be sized and configured such that thesoftened portion 132 buckles against the back side 306 into a flattenedbuckled sleeve portion 138 having a relatively large bearing area. Forexample, the sleeve 104 may be sized and configured such that thesoftened portion 132 buckles into a buckled sleeve portion 138 having aminimum diameter of 1.2 times the sleeve outside diameter 120 (FIG. 3).In this regard, the sleeve 104 may be configured such that the buckledsleeve portion diameter 140 is in the range of from approximately 1.2 to1.5 times the sleeve outside diameter 120 (FIG. 3). However, the sleeve104 may be sized and configured such that the buckled sleeve portiondiameter 140 is larger or smaller than 1.2 to 1.5 times the sleeveoutside diameter 120.

Referring to FIG. 9, shown is the fastener system 100 wherein rotationalforce may be applied to the core bolt 150 using the rotation feature 186provided on the frangible driving provision 180. The upper portion ofthe structure 300 in FIG. 9 represents a maximum grip 310 installationin a structure 300 and the lower portion of the structure 300 in FIG. 9represents a minimum grip 312 installation. In FIG. 9, the buckledsleeve portion 138 is substantially fully formed such that the core bolt150 may be rotated without twisting deformation of the buckled sleeveportion 138 which may otherwise compromise the consistency of tensionpreload from fastener to fastener. The core bolt 150 may be rotatedrelative to the sleeve 104 by engaging the faceted surfaces 188 of therotation feature 186 of the frangible pintail 182 in a manner causingrotation of the core bolt 150 relative to the sleeve 104. For example,an installation tool (not shown) may include a rotational drive bitconfigured to engage the rotation feature 186 on the frangible pintail182.

Advantageously, rotation of the core bolt 150 relative to the sleeve 104results in the application of tension preload in the fastener system 100or an increase in the tension preload induced in the fastener system 100as a result of the axial translation (FIGS. 7-8) of the core bolt 150.In FIG. 9, rotation of the frangible pintail 182 causes the core bolthead 152 to translate back toward the sleeve head 106 as the core boltthreads 160 engage the locking feature 128 on the sleeve tail 126.Tension preload may increase in the fastener system 100 (e.g., in thesleeve 104 and in the core bolt 150) while the core bolt 150 is rotatedrelative to the sleeve 104 until reaching a pre-defined fastener preload316.

Referring to FIG. 10, shown is the fastener system 100 installation fora maximum grip 310 installation and a minimum grip 312 installation in astructure 300. Upon reaching the predefined fastener preload 316 (FIG.9), the frangible driving provision 180 may separate from the core bolthead 152 by fracturing at the interface 198 between the frangiblepintail 182 and the core bolt head 152. For example, the frangiblepintail 182 may separate from the core bolt head 152 due to torsionalload causing a fracture at break groove 184 that may be formed at theinterface 198 between the frangible pintail 182 and the core bolt head152. The frangible pintail 182 may also be separated from the core bolthead 152 by axially translating (e.g., pulling) the frangible drivingprovision 180 until exceeding a tension load capability at the interface198 between the frangible pintail 182 and the core bolt head 152. Stillfurther, the frangible pintail 182 may be separated from the core bolthead 152 by bending the frangible pintail 182 relative to the core bolthead 152 and causing fracturing under bending load.

The fastener preload 316 may comprise tension preload in the core bolt150/sleeve 104 and may correspond to compression preload in thestructure 300 representing clamp-up of one or more components that makeup the structure 300. The fastener system 100 may be configured tocontrol the point (i.e., the fastener preload) at which the frangiblepintail 182 rotatably fractures (e.g., twists) off of the core bolt head152 and may be derived through analysis and/or experimentation. Forexample, fastener preload 316 may be characterized by a quantity ofrevolutions of the frangible pintail 182 relative to the sleeve 104after the buckled sleeve portion 138 is flattened against the back side306 of the structure 300.

Referring to FIGS. 11-14, shown is a configuration of an installationtool 400 as may be implemented for installation of the fastener system100 (FIG. 9). The installation tool 400 may include a housing 402 havinga side wall 408 and a bearing flange 404. A collet 410 may be axiallyslidable within the housing 402 and may bear against a taper 412 thatmay be formed in the housing 402. An ejection spring 418 may be includedwith the installation tool 400 to eject the frangible driving provision180 from the installation tool 400 after the frangible driving provision180 (FIG. 10) or frangible pintail 182 (FIG. 10) fractures off of thecore bolt head 152 (FIG. 10). The collet 410 may be segmented as shownin FIG. 13 to allow the collet 410 segments to radially expand so thatthe collet 410 may be axially moved over the axial translation feature192 (e.g., helical threads 194, annular grooves 196—FIG. 15) that may beformed on the frangible pintail 182 (FIG. 15). A rotational drive member416 such as a hex pin may be axially slidable within the collet 410. Therotational drive member 416 (e.g., hex pin) may be engaged to therotation feature 186 (e.g., hex bore) of the frangible pintail 182 (FIG.15).

Referring to FIG. 12, shown is an end view of the installation tool 400of FIG. 11 and illustrating the sleeve engagement features 406 that maybe included with the bearing flange 404 for engaging anti-rotationfeatures 134 that may be formed on the sleeve head 106 (FIGS. 3-4). FIG.12 further illustrates a hex shape of the rotational drive member 416(e.g., hex pin) for engaging the hex-shaped faceted surfaces 188 (e.g.,hex bore) formed in the frangible pintail 182 (FIG. 15). FIG. 13 is across-sectional end view of the installation tool 400 illustrating thesegmented collet 410 and the rotational drive member 416.

Referring to FIGS. 11-15, during operation, the installation tool 400may be applied over the frangible pintail 182 such that the sleeveengagement features 406 on the bearing flange 404 engage theanti-rotation features 134 of the sleeve head 106. As the installationtool 400 is applied over the frangible pintail 182, the free end of thecollet 410 contacts the free end of the frangible pintail 182 causingthe segmented collet 410 to radially expand and axially move over thehelical threads 194 that may be formed on the frangible pintail 182. Theinstallation tool 400 may include a biasing spring 414 in the housing402 to bias the rotational drive member 416 into the rotation feature186 (e.g., hex-shaped bore) in the frangible pintail 182 as the collet410 is axially moved over the helical threads 194 of the frangiblepintail 182. The biasing spring 414 may have a larger diameter than anouter diameter or width of the rotational drive member 416 such that thebiasing spring 414 may bear against an annular flange 417 formed on therotational drive member 416.

After the bearing flange 404 of the installation tool 400 is seatedagainst the sleeve head 106 and the collet 410 threads are engaged tothe helical threads 194 of the frangible pintail 182, the collet 410 andthe core bolt 150 may be axially translated backward away from the frontside 304 (FIGS. 7-8) of the structure 300. An outer surface of thecollet 410 may bear against the taper 412 formed on the interior of thehousing 402 which may increase a clamping force of the collet 410threads onto the helical threads 194 of the frangible pintail 182. Therotational drive member 416 is configured to initially prevent rotationof the core bolt 150 as the core bolt 150 is axially translated backwardaway from the front side 304 (FIGS. 7-8) by rotation of the collet 410.Rotation of the collet 410 continues until the softened portion 132(FIGS. 7-8) of the sleeve 104 buckles into a flattened shape against theback side 306 of the structure 300 as shown in FIGS. 7-8.

When the flattening of the softened portion 132 (FIGS. 7-8) iscompleted, the rotational drive member 416 may be retracted within a hexbore 419 formed in the collet 410. The collet 410 and the rotationaldrive member 416 may then be rotated (FIG. 9) causing rotation of thecore bolt 150 which causes an increase in tension preload in thefastener system 100 until reaching a pre-defined fastener preload. Thebreak groove 184 in the frangible pintail 182 may be configured toseparate or fracture (FIG. 10) from the core bolt head 152 at thepre-defined fastener preload. The ejection spring 418 may move the outersurface of the collet 410 away from the taper 412 in the housing 402which may allow the segmented collet 410 to expand and release thefrangible pintail 182. The frangible pintail 182 may be ejected from thecollet 410 by the ejection spring 418.

Referring to FIGS. 16-17, shown is a configuration of the frangibledriving provision 180 having an external rotation feature 186. Therotation feature 186 may comprise a pair of tapered flats 422 that maybe sized and configured to be engaged by a complementary rotationaldrive member 416 (not shown) of an installation tool (not shown). Theengagement of the frangible driving provision 180 in FIGS. 16-17 may besimilar to the engagement described for the operation of theinstallation tool 400 shown in FIGS. 11-15.

Referring to FIGS. 18-19, shown is a configuration of an installationtool 400 (FIG. 18) and a complementary frangible driving provision 180(FIG. 19). The installation tool 400 may include interior wrench flats430 configured to engage exterior wrench flats 432 that may be formed onthe frangible driving provision 180. The installation tool 400 mayinclude a collet 410 having annular grooves configured to engagecomplementary annular grooves 196 formed on the frangible drivingprovision 180 for axially translating the core bolt 150 relative to thesleeve 104. The exterior wrench flats 432 of the installation tool 400may then be rotated to rotate the core bolt 150 to apply the desiredtension pre-load to the fastener system 100.

Referring to FIGS. 20-22, shown is a configuration of an installationtool 400 having a segmented collet 410 with interior annular grooves forengaging external annular grooves 196 formed on the frangible drivingprovision 180 for pulling or axially translating the core bolt 150 awayfrom the sleeve 104. FIG. 21 illustrates a pair of interior diametricalflats 440 formed in the collet 410 for engaging a complementary pair ofexterior diametrical flats 442 on the frangible driving provision 180(FIG. 22). Operation of the installation tool 400 in FIGS. 20-22 may besimilar to the operation described above for the installation tool 400shown in FIGS. 11-15.

FIG. 23 is a flow diagram of a method 500 of installing a two-piece,one-sided-installation fastener system 100 (FIG. 1) as disclosed above.Advantageously, the fastener system 100 and method disclosed hereinprovides a means for achieving a relatively high preload in the fastenersystem 100 and provides a relatively large bearing area on the back sideof a structure 300. In addition, the fastener system 100 and methodaccommodates relatively large structure thickness variations due to therelatively large grip range provided by the fastener system 100.

Step 502 of the method 500 of FIG. 23 may comprise inserting a core bolt150 and a sleeve 104 into a hole 302 of a structure 300 such as anaircraft structure 300 having a front side 304 and a back side 306 asshown in FIG. 6. Although the figures illustrate the structure 300 ascomprising a single component, the structure 300 may be comprised of twoor more components through which the fastener system 100 may beinstalled. As described above, the core bolt 150 has a frangible drivingprovision 180 coupled to a core bolt head 152. The frangible drivingprovision 180 may include an axial translation feature 192 (FIG. 1) andthe rotation feature 186 (FIG. 1).

Step 504 of the method 500 of FIG. 23 may comprise translating the corebolt 150 backward away from the front side 304 of the hole 302 as shownin FIGS. 7-8. The core bolt 150 may be translated by engaging the axialtranslation feature 192 of the frangible driving provision 180 as shownin FIGS. 7-8. The sleeve head 106 may be maintained against thestructure 300 to prevent axial translation thereof relative to the hole302. In a configuration, the core bolt 150 may preferably be translatedwithout translating or rotating the sleeve 104 and/or without rotatingthe core bolt 150 relative to the sleeve 104 and preferably withouteither the core bolt 150 or the sleeve 104 rotating relative to the hole302.

Step 506 of the method 500 of FIG. 23 may comprise buckling a softenedportion 132 of the sleeve 104 against the back side 306 of the structure300 to form a buckled sleeve portion 138 as shown in FIGS. 7-8. Thesoftened portion 132 may buckle radially outwardly into an annularsleeve bulb as the core bolt head 152 is translated away from the frontside 304 of the structure 300 as shown in FIGS. 7-8.

Step 508 of the method 500 of FIG. 23 may comprise flattening thebuckled sleeve portion 138 against the back side 306 of the structure300 as shown in FIGS. 7-8. In this regard, the core bolt 150 may begenerally translated along a direction away from the front side 304 ofthe structure 300 until the buckled sleeve portion 138 is generallyflattened against the back side 306 of the structure 300 as shown inFIGS. 7-8. However, the process of buckling the softened portion 132(FIGS. 7-8) may be terminated at any point prior to flattening thereof.

Step 510 of the method 500 of FIG. 23 may comprise rotating the corebolt 150 relative to the sleeve 104 as shown in FIG. 9. The core bolt150 may be rotated by engaging a rotation feature 186 formed on thefrangible driving provision 180 as shown in FIG. 9. In a configuration,the rotation feature 186 may comprise one or more faceted surfaces 188or other rotation feature geometry that may be provided on the frangibledriving provision 180 as shown in FIG. 9. During rotation of the corebolt 150, the core bolt head 152 may move back toward and nest withinthe core bolt pocket 112 in the sleeve head 106 as shown in FIG. 9.During rotation of the core bolt 150, the core bolt threads 160 mayengage the locking feature 128 on the sleeve tail 126 as shown in FIG.9. The method may include preventing rotation of the sleeve 104 relativeto the hole 302 when rotating the core bolt 150 relative to the sleeve104 by engaging an anti-rotation feature 134 (e.g., indentations orprotrusions) that may formed on the sleeve head 106 as shown in FIG. 4.

Step 512 of the method 500 of FIG. 23 may comprise increasing tension inthe fastener in response to rotating the core bolt 150 relative to thesleeve 104 (FIGS. 9-10). Advantageously, after flattening the buckledsleeve portion 138, the sleeve 104 may be restrained against rotationrelative to the hole 302 (FIGS. 9-10) which may facilitate preloadingthe fastener. The preload may increase (e.g., in the sleeve 104 and thecore bolt 150) until reaching a pre-defined fastener preload 316 level(FIG. 9).

Step 514 of the method 500 of FIG. 23 may comprise separating thefrangible driving provision 180 from the core bolt head 152 at thepre-defined fastener preload 316 (FIG. 10). The frangible drivingprovision 180 may be rotated until separating from the core bolt 150 byexceeding the torsional capability of the interface 198 (FIG. 9) betweenthe frangible driving provision 180 and the core bolt head 152, bypulling on the frangible driving provision 180 (FIG. 10) until exceedingthe tension capability at the interface 198, or by bending the frangibledriving provision 180 until exceeding the bending capability of theinterface 198. The process may include separating the frangible drivingprovision 180 from the core bolt head 152 at a break groove 184 (FIG.10) that may be formed at the interface 198 between the frangibledriving provision 180 and the core bolt head 152.

Referring to FIGS. 24-25, configurations of the disclosure may bedescribed in the context of an aircraft manufacturing and service method600 and an aircraft 602 as shown in FIG. 25. During pre-production,exemplary method 600 may include specification and design 604 of theaircraft 602 and material procurement 606. During production, componentand subassembly manufacturing 608 and system integration 610 of theaircraft 602 takes place. Thereafter, the aircraft 602 may go throughcertification and delivery 612 in order to be placed in service 614.While in service by a customer, the aircraft 602 is scheduled forroutine maintenance and service 616 (which may also includemodification, reconfiguration, refurbishment, and so on)

Each of the processes of exemplary method 600 may be performed orcarried out by a system integrator, a third party, and/or an operator(e.g., a customer). For the purposes of this description, a systemintegrator may include, without limitation, any number of aircraftmanufacturers and major-system subcontractors; a third party mayinclude, without limitation, any number of venders, subcontractors, andsuppliers; and an operator may be an airline, leasing company, militaryentity, service organization, and so on.

As shown in FIG. 25, the aircraft 602 produced by exemplary method 600may include an airframe 618 with a plurality of systems 620 and aninterior 622. Examples of high-level systems 620 include one or more ofa propulsion system 624, an electrical system 626, a hydraulic system628, and an environmental system 630. Any number of other systems may beincluded. Although an aerospace example is shown, the principles of thedisclosure may be applied to other industries, such as the automotiveindustry.

Apparatus and methods configured herein may be employed during any oneor more of the processes of the aircraft manufacturing and servicemethod 600. For example, components or subassemblies corresponding toproduction process 608 may be fabricated or manufactured in a mannersimilar to components or subassemblies produced while the aircraft 602is in service 614. Also, one or more apparatus configurations, methodconfigurations, or a combination thereof may be utilized during theproduction processes 608 and 610, for example, by expediting assembly ofor reducing the cost of an aircraft 602. Similarly, one or more ofapparatus configurations, method configurations, or a combinationthereof may be utilized while the aircraft 602 is in service, forexample and without limitation, to maintenance and service 616.

Many modifications and other configurations of the disclosure will cometo mind to one skilled in the art, to which this disclosure pertains,having the benefit of the teachings presented in the foregoingdescriptions and the associated drawings. The configurations describedherein are meant to be illustrative and are not intended to be limitingor exhaustive. Although specific terms are employed herein, they areused in a generic and descriptive sense only and not for purposes oflimitation.

What is claimed is:
 1. A method of installing a two-piece,one-sided-installation fastener system, comprising: inserting a corebolt and a sleeve into a hole of a structure having a front side and aback side, the core bolt having a frangible driving provision coupled toa core bolt head; translating the core bolt backward away from the frontside of the hole without rotating the core bolt relative to the sleeve;buckling a softened portion of the sleeve to form a single buckledsleeve portion; flattening the buckled sleeve portion against the backside of the hole; and rotating the core bolt relative to the sleeve toapply tension in the fastener system independent of translating the corebolt backward away from the front side of the hole.
 2. The method ofclaim 1, further comprising the step of: separating the frangibledriving provision from the core bolt head at a pre-defined fastenerpreload.
 3. The method of claim 2, wherein the step of separating thefrangible driving provision from the core bolt head includes at leastone of: exceeding a torsional capability of an interface between thefrangible driving provision and the core bolt head; axially pulling onthe frangible driving provision until exceeding a tension capability atthe interface; and bending the frangible driving provision untilexceeding a bending capability of the interface.
 4. The method of claim3, wherein the step of separating the frangible driving provision fromthe core bolt head comprises: separating the frangible driving provisionfrom the core bolt head at a break groove formed at the interface. 5.The method of claim 1, wherein: the softened portion comprises alocalized annealed portion extending along a portion of a sleeve length.6. The method of claim 1, wherein the step of buckling the softenedportion of the sleeve includes: buckling the softened portion of thesleeve radially outwardly into an annular sleeve bulb.
 7. The method ofclaim 6, wherein the step of buckling the softened portion of the sleeveincludes: buckling the softened portion until the buckled sleeve portionhas a minimum diameter of approximately 1.2 times a sleeve outsidediameter when the buckled sleeve portion is buckled against thestructure.
 8. The method of claim 1, wherein the step of translating thecore bolt further comprises: engaging an axial translation featureformed on the frangible driving provision.
 9. The method of claim 1,wherein the step of translating the core bolt further comprises:maintaining a sleeve head against the structure in a manner preventingaxial translation of the sleeve relative to the hole.
 10. The method ofclaim 1, wherein the step of translating the core bolt further includes:translating the core bolt without translating or rotating the sleeverelative to the hole.
 11. The method of claim 1, wherein the step ofrotating the core bolt comprises: engaging a rotation feature formed onthe frangible driving provision.
 12. The method of claim 1, wherein thestep of rotating the core bolt includes: engaging core bolt threads witha locking feature formed in the sleeve; and restricting rotation of thecore bolt relative to the sleeve in response to engaging the lockingfeature.
 13. The method of claim 1, wherein the step of rotating thecore bolt relative to the sleeve includes: preventing rotation of thesleeve relative to the hole.
 14. The method of claim 13, wherein thestep of preventing rotation of the sleeve relative to the hole includes:engaging an anti-rotation feature on a sleeve head of the sleeve. 15.The method of claim 14, wherein the step of engaging the anti-rotationfeature on the sleeve head includes: engaging at least one ofindentations and protrusions on the sleeve head.
 16. The method of claim1, wherein the step of rotating the core bolt relative to the sleeveincludes: nesting the core bolt head in a core bolt pocket in a sleevehead of the sleeve.
 17. The method of claim 1, wherein the step ofinserting a core bolt and a sleeve into a hole of a structure comprises:inserting the core bolt and the sleeve into a hole of an aircraftstructure.
 18. A method of installing a two-piece,one-sided-installation fastener system, comprising: inserting a corebolt and a sleeve into a hole of a structure having a front side and aback side, the core bolt having a frangible driving provision coupled toa core bolt head, the sleeve having a sleeve head; axially pulling onthe frangible driving provision; translating the core bolt backward awayfrom the front side of the hole without rotating the core bolt relativeto the sleeve and while maintaining the sleeve head against thestructure; buckling a softened portion of the sleeve against the backside of the structure to form a single buckled sleeve portion;flattening the single buckled sleeve portion against the back side ofthe hole; and rotating the core bolt relative to the sleeve to applytension to the fastener system without axially translating the core boltrelative to the sleeve.